I've been treated badly over that too.... One day I was talking about a music album of a not-so-well-known band and I shared, of course, the cover image of the album and said what it was, what album it came from, year, author, producer, etc., and some curator was angry with me because I had, and it was my obligation, to post a link to the original place where I had gotten it from.

And he was also very emphatic that I could not use any image I wanted unless I had the license. I would probably have to pay dozens of euros just to be able to acquire a use license for those cover images... For a blog post?